1. Field of the Invention
The present invention relates to a surface treatment system (e.g., serial (continuous) plating system) and a workpiece-holding jig.
2. Description of the Related Art
A serial plating system that serially (continuously) transfers workpieces (e.g., circuit boards) in a plating tank has been known as a surface treatment system such as an electroplating system that plates the surface of a workpiece. The workpiece is suspended from a transfer jig that is transferred along a feed rail, and serially transferred in the plating tank while current is supplied to the workpiece from the feed rail via the transfer jig. Anodes are disposed in the plating tank on either side of a transfer path of the workpiece (i.e., cathode). An electric field is formed between the cathode and the anode to electrolyze the plating solution and plate the surface of the workpiece.
A structure has been known in which the feed rail extends in parallel to the longitudinal direction of the plating tank at a position offset from a position above the plating tank (see Japanese Patent No. 3591721) instead of disposing the feed rail above the plating tank (see Japanese Patent No. 3025254). This makes it possible to prevent a situation in which dust that occurs when the transfer jig slides on the feed rail is mixed into the plating tank.
A surface treatment system such as a serial plating system is configured so that a workpiece is suspended from a workpiece-holding jig, and serially transferred in a solution contained in a surface treatment tank. The workpiece-holding jig normally holds the upper side (end) of the workpiece in a suspended state (see JP-A-2009-132956).
The workpiece-holding jig also has a function of setting the workpiece as a cathode with respect to an anode disposed in the surface treatment tank. An electric field is formed between the cathode and the anode to electrolyze the plating solution and plate the surface of the workpiece. Therefore, a chuck member that holds the upper side (end) of the workpiece is formed using a conductive member, and the workpiece is set as the cathode through the workpiece-holding jig.
In Japanese Patent No. 3025254, the transfer jig and the workpiece are suspended and stably supported right under the feed rail. On the other hand, when disposing the feed rail at a position offset from a position above the plating tank (see Japanese Patent No. 3591721), the center of gravity of the transfer jig and the workpiece is offset from the perpendicular line that passes through the feed rail, so that an unnecessary moment acts on the transfer jig.
Therefore, the transfer jig disclosed in Japanese Patent No. 3591721 has a complex structure as compared with the jig disclosed in Japanese Patent No. 3025254 in order to suppress a problem due to an unnecessary moment. For example, Japanese Patent No. 3591721 provides a removal prevention rail that prevents removal of the transfer jig on the side surface of the feed rail. Therefore, the structure of the feed rail also becomes complex.
If the workpiece is tilted to intersect the transfer direction when viewed from above when the workpiece that is held by the transfer jig advances in the treatment solution, the workpiece may be bent due to the treatment solution, so that the commercial value of the workpiece may be impaired. If a vertical motion of the transfer jig occurs when the workpiece that is held by the transfer jig advances in the treatment solution, the electrical contact between the feed rail and the transfer jig may be impaired, so that the plating quality may deteriorate. In order to prevent such a situation, it is necessary to employ a complex structure for stabilizing the travel of the transfer jig.
It was also found that it is difficult to ensure the in-plane uniformity of the surface treatment of the workpiece when providing only a current-carrying path that is connected to the upper side (end) of the workpiece (see JP-A-2009-132956).